The present invention includes a weighted training shoe insert and a method of fabricating a weighted training shoe insert having a higher than 1.0 specific gravity and a low Shore A Durometer. Weighted inserts have been attempted in the past, but have limited use due to fabrication problems and the difficulty of obtaining a proper weight with a desired hardness or Durometer.
Weighted inserts can be fabricated with a two-component thermoset urethane system with powdered metal added to liquid urethane components to increase the specific gravity of the part. The problem with casting inserts in this manner is that the specific gravity of the desired compound is limited, resulting in much less weight than desired for the insert. Due to the low specific gravity, to achieve a sufficient weight for the insert, a cast insert must be thicker than desirable.
The specific gravity is limited in the casting process because the addition of the powdered metal significantly increases the viscosity of the two-component urethane. Above a certain viscosity, the material can no longer be cast easily. The estimated specific gravity of inserts of this type is about 3.0 to 3.5. Increasing the specific gravity to the high end of this range greatly increases the difficulty in the casting process, because of the significant viscosity increase referred to above and this result requires additional, more costly equipment. Thus, it can be seen that achieving the desired higher specific gravity is severely limited by the process.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
It is an object of the present invention to provide new and improved athletic training shoe weighted inserts and a method of fabrication.
Another object of the present invention is to provide new compositions that can be easily manufactured into improved athletic training shoe weighted inserts with a desired specific gravity and a low Shore A Durometer to maximize comfort.
Another object of the present invention is to provide a new and improved method of manufacturing weighted athletic training inserts or insoles that have a higher than 1.0 specific gravity for athletic training and physical therapy.